Reduction gear unit

ABSTRACT

There is provided a reduction gear unit including: a pinion; a bearing that is located on each of both sides of the pinion; a large gear that meshes with the pinion; a gear case that stores therein lubricant oil, and accommodates the pinion and the gear; and pinion bearing caps each of which includes an annular portion, wherein the annular portion extends from outside of the gear case toward inside thereof and parallel to a pinion shaft, and includes an end portion in which an end surface in an extending-direction is provided on a side of the pinion with respect to an extended line of a gear-side end surface of an inner race of the bearing, and an inner peripheral surface of the end portion is formed so that a diameter is decreased from a gear-side end surface of an outer race toward the end surface.

FIELD

The present invention relates to a reduction gear unit mainly used fordriving a railway vehicle (hereinafter, simply “gear unit”), and to abearing provided in the interior of the gear unit.

BACKGROUND

A conventional gear unit is configured by including a high-speed-sidepinion that is fixed to a pinion shaft provided parallel to an axle; alow-speed-side large gear that is fixed to the axle, formed with adiameter larger than a diameter of the pinion, and meshes with thepinion; and a gear case that accommodates therein the pinion and thelarge gear. This gear unit with the axle is installed on a truck frame,and transmits a rotational torque from a traction motor to the axle torotate wheels mounted on the axle. The pinion and the large gear areheld in the gear case by bearings located on each of both sides of thesegears in order that their axial lines are parallel to each other, andmesh with each other. As the bearing of this gear unit, a tapered rollerbearing capable of supporting a radial load and a thrust load, andhaving a large allowable load capacity is used. This bearing isaccommodated in a bearing cap fitted to the gear case for ease ofmaintenance. At the bottom of the gear case, a necessary amount oflubricant oil is stored. The height of the lubricant oil level ismanaged in order that a part of the large gear is dipped in thelubricant oil.

The lubricant oil stored at the bottom of the gear case, is drawn up byrotations of the large gear and is supplied to a meshing part betweenthe large gear and the pinion (hereinafter, “meshing part”), tolow-speed-side bearings provided on each of both sides of the largegear, to high-speed-side bearings provided on each of both sides of thepinion, and the like.

To be more specific, first in the meshing part, lubricant oil sticks totooth flanks of the large gear and therefore this lubricant oil isdirectly supplied to the meshing part when the large gear rotates. Next,in the low-speed-side bearing, lubricant oil drawn up by the toothflanks of the large gear and splashing within the gear case, iscollected by an oil pan provided at the top of the gear case. Thecollected lubricant oil is supplied into the bearing from asmall-diameter-side end surface of a tapered roller (hereinafter, simply“roller”) in the low-speed-side bearing. Next, the high-speed-sidebearing is explained. Because the pinion rotates at high speed, it isnecessary to directly supply lubricant oil particularly to an area wherea large-diameter-side end surface of a roller of the high-speed-sidebearing (a pinion-side surface of the roller) comes into contact with alarge-diameter-side flange portion of an inner race of thehigh-speed-side bearing.

For example, in a typical conventional gear unit in Patent Literature 1mentioned below, a pinion and a larger gear are accommodated in asemi-hermetic gear case with these gears meshed with each other, asshown in FIG. 1 of the Patent Literature 1. The lubricant oil in thegear case is drawn up by rotations of the large gear. Further, in thisconventional gear unit, an opening provided on the gear side between aninner race and an outer race of a high-speed-side bearing is arrangedschematically on the lateral side of a meshing part. That is, theopening of the high-speed-side bearing extends in the width (thickness)direction of each gear and is located close to the pinion with respectto an intermeshing pitch line.

With such a configuration, the lubricant oil sticking between teethformed on the large gear, is pushed out to both sides of the meshingpart (in the width direction of each gear) by the meshing of the largegear and the pinion. The lubricant oil, having been pushed out, entersinto the high-speed-side bearing from the opening of the bearing, and issupplied to a contact portion between the large-diameter-side endsurface of the roller and the large-diameter-side flange portion of theinner race. As described above, in the typical gear unit according tothe conventional technique in Patent Literature 1 mentioned below, theopening of the high-speed-side bearing is arranged schematically on thelateral side of the meshing part. Therefore, lubricant oil iscontinuously supplied to areas where lubricant oil is required, andoverheating and seizure of the bearing are suppressed.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Utility Model Application No. 6-74551

SUMMARY Technical Problem

However, the typical gear unit according to the conventional techniquein Patent Literature 1 mentioned above has the following problems. Asdescribed above, according to the conventional technique, the opening ofthe high-speed-side bearing is arranged schematically on the lateralside of the meshing part. However, depending on the setting on themodule of a gear and on the setting on the number of teeth of a pinion,the opening of the high-speed-side bearing cannot be arranged on thelateral side of the meshing part. For example, there is a case where theopening is provided on the large-gear side with respect to theintermeshing pitch line. In that case, lubricant oil pushed out from themeshing part, hits a gear-side end surface of the inner race of thehigh-speed-side bearing. As a result, a supply of the lubricant oil intothe bearing becomes insufficient and overheating and seizure of thebearing can be caused.

An object of the present invention is to provide a gear unit and abearing of the gear unit, which can stably supply lubricant oil to theinterior of the bearing, regardless of the setting on a module of a gearand the setting on the number of teeth of a pinion.

Solution to Problem

There is provided a bearing according to an aspect of the presentinvention including an inner race that rotates integrally with a pinionshaft provided with a pinion, an outer race, and a plurality of rollersthat are arranged rotatably between the inner race and the outer racewhile maintaining a predetermined spacing to one another in a rotationdirection of the inner race, wherein each of the rollers includes alarge-diameter-side end surface that is provided on a side of thepinion, and a small-diameter-side end surface that is provided on anopposite side to the side of the pinion, and is configured to have ashape tapered from the large-diameter-side end surface toward thesmall-diameter-side end surface, the outer race includes a conicalraceway surface that is provided on an inner peripheral side, and thatcomes into contact with an outer peripheral surface of each of therollers, the inner race includes a conical raceway surface that isprovided on an outer peripheral side thereof and that comes into contactwith the outer peripheral surface of each of the rollers, asmall-diameter-side flange portion that is provided on an opposite sideto the pinion with respect to an extended line of thesmall-diameter-side end surface of each of the rollers, and alarge-diameter-side flange portion that is provided on the side of thepinion with respect to an extended line of the large-diameter-side endsurface of each of the rollers, and extends in a direction from theinner race to the outer race to be close to a gear-side end surface ofthe outer race while enclosing the large-diameter-side end surface ofeach of the rollers, and forms an opening between the gear-side endsurface and the large-diameter-side flange portion, and in thelarge-diameter-side flange portion of the inner race, a plurality ofthrough holes that are formed with a predetermined spacing to oneanother in a rotation direction of the inner race, and that connect froma gear-side end surface of the inner race toward outer peripheral edgesof the large-diameter-side end surfaces of the rollers are provided.

Advantageous Effects of Invention

According to the present invention, a plurality of through holes thatconnect from a gear-side end surface of an inner race toward an outerperipheral edge of a large-diameter-side end surface of a roller areprovided. Therefore, lubricant oil can be stably supplied to theinterior of a bearing, regardless of the setting on a module of a gearand the setting on the number of teeth of a pinion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a truck for a vehicle in which gearunits according to a first embodiment of the present invention areinstalled.

FIG. 2 is an external view of a gear unit as viewed from a directionindicated by an arrow A shown in FIG. 1.

FIG. 3 is a cross-sectional view of the gear unit as viewed from adirection indicated by an arrow B shown in FIG. 2.

FIG. 4 depicts a detailed structure of a bearing shown in FIG. 3.

FIG. 5 is a first diagram for explaining a bearing used in aconventional gear unit and a flow of lubricant oil.

FIG. 6 is a second diagram for explaining the bearing used in theconventional gear unit and a flow of the lubricant oil.

FIG. 7 depicts an internal structure of a gear unit according to asecond embodiment of the present invention.

FIG. 8 depicts an internal structure of a gear unit according to a thirdembodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments of a reduction gear unit and a bearing accordingto the present invention will be explained below in detail withreference to the accompanying drawings. The present invention is notlimited to the embodiments.

First Embodiment

FIG. 1 is a schematic diagram of a truck for a vehicle in which gearunits 100 a and 100 b according to a first embodiment of the presentinvention are installed. FIG. 2 is an external view of a gear unit 100as viewed from a direction indicated by an arrow A shown in FIG. 1.

In FIG. 1, the truck for a vehicle is configured to include tractionmotors 20 a and 20 b that are installed on a truck frame 30; axles 23 aand 23 b that are rotatably provided on the truck frame 30, and thathave wheels 41 fitted to both ends of the axles 23 a and 23 b; and thegear units 100 a and 100 b that are respectively coupled with thetraction motors 20 a and 20 b and with the axles 23 a and 23 b, and thatrespectively reduce the rotating speed of the traction motors 20 a and20 b to transmit driving force to the axles 23 a and 23 b.

The axle 23 a is mounted to the gear unit 100 a, and the axle 23 b ismounted to the gear unit 100 b. A rotor shaft of the traction motor 20 aand a pinion shaft 9 a of the gear unit 100 a are flexibly coupled by aflexible coupling 24 a. A rotor shaft of the traction motor 20 b and apinion shaft 9 b of the gear unit 100 b are flexibly coupled by aflexible coupling 24 b.

The gear unit 100 a reduces the rotating speed of the traction motor 20a and transmits the reduced rotating speed to the axle 23 a. Arotational torque of the traction motor 20 a is transmitted to the gearunit 100 a through the flexible coupling 24 a to rotate the axle 23 aand the wheels 41. Similarly, the gear unit 100 b reduces the rotatingspeed of the traction motor 20 b and transmits the reduced rotatingspeed to the axle 23 b. A rotational torque of the traction motor 20 bis transmitted to the gear unit 100 b through the flexible coupling 24 bto rotate the axle 23 b and the wheels 41.

The gear unit 100 shown in FIG. 2 is configured to include a pinion 10that is fixed to a pinion shaft 9 provided parallel to an axle 23; alarge gear 11 that is fixed to the axle 23, formed with a diameterlarger than a diameter of the pinion 10, and meshes with the pinion 10;and a gear case 1 that stores therein a necessary amount of lubricantoil 16, and accommodates therein the pinion 10 and the large gear 11.

On the left side of the gear case 1 (on the left side in FIG. 2), apinion bearing cap 21 is fitted. On the right side of the gear case 1(on the right side in FIG. 2), a large-gear-side bearing cap 26 isfitted. The pinion bearing cap 21 and the large-gear-side bearing cap 26are located on a traction motor-side surface of the gear case 1, andsurround and support respective bearing outer races. The height of alubricant oil level 17 is managed by an oil level gauge 18 in order thata part of the large gear 11 is dipped in the lubricant oil 16.

FIG. 3 is a cross-sectional view of the gear unit as viewed from adirection indicated by an arrow B shown in FIG. 2. FIG. 3 depicts aninternal configuration of the gear unit 100, which focuses on the pinion10 that is fixed to the pinion shaft 9 and on a high-speed-side bearing(a bearing 4) located on each of both sides of the pinion 10. FIG. 4depicts a detailed structure of the bearing shown in FIG. 3.

The bearing 4 is configured to include an inner race 6 that rotatesintegrally with the pinion shaft 9, an outer race 5 that is provided inthe gear case 1, and a plurality of rollers 7 that are rotatablyarranged between the inner race 6 and the outer race 5 while maintaininga predetermined spacing to one another in the rotation direction of theinner race 6 by a bearing cage 8. The bearing cage 8 prevents therollers 7 from coming off the bearing 4, and also holds the rollers 7 atequal spacing in the bearing 4 to prevent the rollers 7 from coming intocontact with each other.

On a surface 1 a of the gear case 1 on the traction motor side shown inFIG. 3, the pinion bearing cap 21 that is detachably fixed by a fastener12 (for example, a bolt) screwed into the surface 1 a on the tractionmotor side is located, in consideration of the maintainability of thebearing 4. The pinion bearing cap 21 is configured to include an annularportion 21 b that is interposed between the gear case 1 and an outerperipheral surface 5 b of the outer race 5, and that surrounds the outerperipheral surface 5 b. The annular portion 21 b extends from outside ofthe gear case 1 toward the inside and parallel to the pinion shaft 9,while enclosing the outer peripheral surface 5 b of the outer race 5. Aninner peripheral portion 21 a of the annular portion 21 b comes intocontact with the outer peripheral surface 5 b of the outer race 5. Anend surface 21 c of the annular portion 21 b on the inside of the gearcase 1 is provided before an extended line of a gear-side end surface 6b of the inner race 6, as an example. The outer race 5 held by thepinion bearing cap 21 is capable of separating from the rollers 7 andthe inner race 6 when the fastener 12 is removed. With thisconfiguration, it is possible to perform maintenance of the bearing 4.

Between the pinion bearing cap 21 and the gear case 1, a shim set 13that includes several shims and has an appropriate clearance isincorporated in order to provide an appropriate clearance to the partsof the bearing 4. By using the shim set 13, it is possible to continuerotations without causing seizure of the bearing 4 even when therespective portions of the bearing 4 expand due to a temperature riseduring operation. The clearance of the shim set 13 is managed with adefined upper limit value of the clearance in order to prevent thepinion shaft 9 from being largely inclined. In the pinion bearing cap21, a labyrinth seal is provided at a boundary portion between thepinion bearing cap 21 and the pinion shaft 9 in order to prevent a partof the lubricant oil 16 in the gear case 1 from leaking outside the gearcase 1, and also to prevent outside dust and the like from entering intothe gear case 1.

On a surface 1 b of the gear case 1 shown in FIG. 3, which is oppositeto the traction motor side, a pinion bearing cap 22 that is detachablyfixed by the fastener 12 (for example, a bolt) screwed into the surface1 b opposite to the traction motor side is located, in consideration ofthe maintainability of the bearing 4. The pinion bearing cap 22 isconfigured to include an annular portion 22 b that is interposed betweenthe gear case 1 and the outer peripheral surface 5 b of the outer race5, and that surrounds the outer peripheral surface 5 b. The annularportion 22 b extends from outside of the gear case 1 toward the insideand parallel to the pinion shaft 9, while enclosing the outer peripheralsurface 5 b of the outer race 5. An inner peripheral portion 22 a of theannular portion 22 b comes into contact with the outer peripheralsurface 5 b of the outer race 5. An end surface 22 c of the annularportion 22 b on the inside of the gear case 1 is provided before theextended line of the gear-side end surface 6 b of the inner race 6, asan example. The outer race 5 held by the pinion bearing cap 22 iscapable of separating from the rollers 7 and the inner race 6 when thefastener 12 is removed. With this configuration, it is possible toperform maintenance of the bearing 4.

In FIG. 4, the roller 7 includes a large-diameter-side end surface 7 bthat is provided on the side of the pinion 10 in the bearing 4, and asmall-diameter-side end surface 7 a that is provided on the oppositeside to the side of the pinion 10 in the bearing 4. The roller 7 isconfigured to have a shape tapered from the large-diameter-side endsurface 7 b toward the small-diameter-side end surface 7 a.

The outer race 5 is configured to include a conical raceway surface 5 athat is provided on the inner peripheral side, and that comes intocontact with an outer peripheral surface 7 c of the roller 7.

The inner race 6 is configured to include a conical raceway surface 6 cthat is provided on the outer peripheral side, and that comes intocontact with the outer peripheral surface 7 c of the roller 7, asmall-diameter-side flange portion 6 d, a large-diameter-side flangesurface 6 h, and a large-diameter-side flange portion 6 g.

The small-diameter-side flange portion 6 d is provided on the oppositeside to the side of the pinion 10 in the bearing 4 with respect to anextended line of the small-diameter-side end surface 7 a of the roller7.

The large-diameter-side flange portion 6 g is provided on the side ofthe pinion 10 in the bearing 4 with respect to an extended line of thelarge-diameter-side end surface 7 b of the roller 7. Thelarge-diameter-side flange portion 6 g extends in the direction from theinner race 6 to the outer race 5, while enclosing thelarge-diameter-side end surface 7 b of the roller 7, to be close to agear-side end surface 5 d of the outer race 5, thereby forming anopening 4 a between the gear-side end surface 5 d and thelarge-diameter-side flange portion 6 g.

The large-diameter-side flange surface 6 h that comes into contact withthe large-diameter-side end surface 7 b of the roller 7 and guides theroller 7, is provided on the side of the roller 7 in thelarge-diameter-side flange portion 6 g of the inner race 6. Thelarge-diameter-side flange surface 6 h of the inner race 6 comes intocontact with the large-diameter-side end surface 7 b of the roller 7,thereby restricting movement of the roller 7 in the roller-shaftdirection.

In the large-diameter-side flange portion 6 g of the inner race 6, aplurality of through holes 6 a that are formed with a predeterminedspacing to one another in the rotation direction of the inner race 6,and that connect from the gear-side end surface 6 b of the inner race 6toward an outer peripheral edge 7 d of the large-diameter-side endsurface 7 b of the roller 7 are provided. The lubricant oil 16 pushedout from a meshing part 19 between the pinion 10 and the large gear 11,flows into a gear side opening 6 e of the through hole 6 a. Thelubricant oil 16, having flown into the through hole 6 a, is drainedfrom a roller side opening 6 f provided at the intersecting part of theraceway surface 6 c of the inner race 6 and the large-diameter-sideflange surface 6 h of the inner race 6.

When the length from an inner peripheral surface 6 i of the inner race 6to the gear side opening 6 e of the through hole 6 a is represented asL1, and the length from the inner peripheral surface 6 i of the innerrace 6 to the roller side opening 6 f of the through hole 6 a isrepresented as L2, the through hole 6 a shown in FIG. 4 is configured sothat a value of L1 is smaller than a value of L2. That is, the throughhole 6 a shown in FIG. 4 is inclined so as to be away from the axialline of the pinion shaft 9 as the through hole 6 a extends from thegear-side end surface 6 b of the inner race 6 toward the outerperipheral edge 7 d of the large-diameter-side end surface 7 b of theroller 7. Therefore, the lubricant oil 16, staying adjacent to thegear-side end surface 6 b, is forcibly supplied to the outer peripheraledge 7 d of the large-diameter-side end surface 7 b of the roller 7through the through hole 6 a due to a centrifugal force generated whenthe inner race 6 rotates.

Next, movement of the lubricant oil 16 is explained. The lubricant oil16 stored at the bottom of the gear case 1, is drawn up by rotations ofthe large gear 11 and is supplied to the meshing part 19 between thelarge gear 11 and the pinion 10, to a low-speed-side bearing (not shown)provided on each of both sides of the large gear 11, to the bearing 4provided on each of both sides of the pinion 10, and the like. Forexample, lubricant oil, sticking to tooth flanks of the large gear 11,is supplied directly to the meshing part 19. Next, concerning thelow-speed-side bearing, the lubricant oil 16 drawn up by the toothflanks of the large gear 11 and splashing within the gear case 1, iscollected by an oil pan (not shown) provided on the top of the gear case1. The collected lubricant oil 16 is supplied from a small-diameter-sideend surface of a roller within the low-speed-side bearing into thebearing.

Next, an oil supply to the bearing 4 is explained using the symbols a tod shown in FIGS. 3 and 4. (a) The lubricant oil 16, sticking betweenteeth of the large gear 11, is pushed out to both sides of the pinion 10due to the meshing of the large gear 11 and the pinion 10. (b) Thelubricant oil 16, pushed out from the meshing part 19, passes throughthe through hole 6 a formed in the inner race 6. (c) A part of thelubricant oil 16, having passed through the through hole 6 a, issupplied to a contact portion between the large-diameter-side flangesurface 6 h of the inner race 6 and the large-diameter-side end surface7 b of the roller 7. (d) A part of the lubricant oil 16, having passedthrough the through hole 6 a, is also supplied to a contact portionbetween the raceway surface 6 c of the inner race 6 and the outerperipheral surface 7 c of the roller 7.

FIG. 5 is a first diagram for explaining a bearing 40 used in aconventional gear unit and a flow of the lubricant oil 16. FIG. 6 is asecond diagram for explaining the bearing 40 used in the conventionalgear unit and a flow of the lubricant oil 16.

In FIG. 5, in the conventional gear unit, the opening 4 a of the bearing40 extends in the width (thickness) direction of a pinion, and isprovided close to the pinion 10 on an intermeshing pitch line 14.Further, no through hole is provided in an inner race 60 of the bearing40, unlike the inner race 6 according to the first embodiment. Thelubricant oil 16, pushed out from the meshing part 19, is supplied fromthe opening 4 a of the bearing 40 to the interior of the bearing 40. Asdescribed above, in the gear unit according to the conventionaltechnique, the opening 4 a of the bearing 40 is arranged schematicallyon the lateral side of the meshing part 19.

However, depending on the setting on the module of the pinion 10 and onthe setting on the number of teeth of the pinion 10, the opening 4 a ofthe bearing 40 is not arranged on the lateral side of the meshing part19, as shown in FIG. 6. The opening 4 a of the bearing 40 shown in FIG.6 is provided on the side of the large gear 11 with respect to theintermeshing pitch line 14. Therefore, the lubricant oil 16, pushed outfrom the meshing part 19, hits the gear-side end surface 6 b of theinner race 6. As a result, a supply of the lubricant oil 16 into thebearing 40 becomes insufficient and overheating and seizure of thebearing 40 may occur.

In the bearing 4 according to the first embodiment, the through holes 6a are provided in the large-diameter-side flange portion 6 g of theinner race 6. Therefore, the lubricant oil 16 pushed out from themeshing part 19 between the pinion 10 and the large gear 11, is suppliedthrough the through holes 6 a into the bearing 4. As a result,overheating and seizure of the bearing 4 are suppressed.

The through holes 6 a of the bearing 4 according to the first embodimentare configured so that a value of L1 is smaller than a value of L2.However, the configuration of the through holes 6 a is not limitedthereto. For example, the through holes 6 a can also be configured sothat a value of L1 is equal to a value of L2 (L1=L2). In the case ofsuch a configuration, an oil supply to the outer peripheral edge 7 d ofthe roller 7 is still possible, although an oil supply effect that isobtained by a centrifugal force generated when the inner race 6 rotatesis reduced.

As explained above, in the bearing 4 according to the first embodiment,the roller 7 includes the large-diameter-side end surface 7 b that isprovided on the side of the pinion 10, and the small-diameter-side endsurface 7 a that is provided on the opposite side to the side of thepinion 10, and the roller 7 is also configured to have a shape taperedfrom the large-diameter-side end surface 7 b toward thesmall-diameter-side end surface 7 a. The outer race 5 includes theconical raceway surface 5 a that is provided on the inner peripheralside and comes into contact with the outer peripheral surface 7 c of theroller 7. The inner race 6 includes the conical raceway surface 6 c thatis provided on the outer peripheral side thereof and comes into contactwith the outer peripheral surface 7 c of the roller 7; thesmall-diameter-side flange portion 6 d that is provided on the oppositeside to the pinion 10 with respect to the extended line of thesmall-diameter-side end surface 7 a of the roller 7; and thelarge-diameter-side flange portion 6 g that is provided on the side ofthe pinion 10 with respect to the extended line of thelarge-diameter-side end surface 7 b of the roller 7, and that extends inthe direction from the inner race 6 to the outer race 5, while enclosingthe large-diameter-side end surface 7 b of the roller 7, to be close tothe gear-side end surface 5 d of the outer race 5, thereby forming theopening 4 a between the gear-side end surface 5 d and thelarge-diameter-side flange portion 6 g. The through holes 6 a that areformed with a predetermined spacing to one another in the rotationdirection of the inner race 6, and that connect from the gear-side endsurface 6 b of the inner race 6 toward the outer peripheral edge 7 d ofthe large-diameter-side end surface 7 b of the roller 7 are provided inthe large-diameter-side flange portion 6 g of the inner race 6.Therefore, it is possible to continuously supply the lubricant oil 16 toareas where the lubricant oil 16 is required through the through holes 6a, regardless of the setting of the module of a gear and the setting ofthe number of teeth of a pinion.

Further, in the bearing 4 according to the first embodiment, the throughholes 6 a provided in the inner race 6 have a shape satisfying therelationship expressed as L1<L2. Therefore, the lubricant oil 16,staying adjacent to the gear-side end surface 6 b, is forcibly suppliedto the outer peripheral edge 7 d of the large-diameter-side end surface7 b of the roller 7 through the through holes 6 a by a centrifugal forcegenerated when the inner race 6 rotates. As a result, overheating andseizure of the bearing 4 can be suppressed, and also it is possible touse the bearing 4 for a long period of time.

Second Embodiment

FIG. 7 depicts an internal structure of a gear unit according to asecond embodiment of the present invention. Differences between thefirst embodiment and the second embodiment are as follows. The annularportions 21 b and 22 b of the pinion bearing caps 21 and 22 arerespectively provided inside the gear case 1 so as to extend parallel tothe pinion shaft 9, and an inner peripheral surface of each extendingpart of the annular portions 21 b and 22 b is formed into a taperedshape in which the inner diameter on the side of the bearing 4 is largerthan the distal-end-side inner diameter on the tip portion side.Elements of the present embodiment that are identical to those of thefirst embodiment are denoted by like reference signs and explanationsthereof will be omitted, and elements different from the firstembodiment are explained.

The annular portion 21 b of the pinion bearing cap 21, shown in FIG. 7,is provided inside the gear case 1 so as to extend in parallel to thepinion shaft 9, and includes an end portion 21 e in which an end surface21 c in an extending-direction is provided on the side of the pinion 10with respect to the extended line of the gear-side end surface 6 b ofthe inner race 6. By forming the annular portion 21 b as describedabove, even when a part of the lubricant oil 16 pushed out from themeshing part 19, hits a side surface (the gear-side end surface 6 b) ofthe inner race 6, and drops toward the end portion 21 e of the annularportion 21 b, it is still possible to supply the lubricant oil 16 to theopening 4 a of the bearing 4.

Further, the diameter of an inner peripheral edge 21 g (the innerdiameter on the side of the bearing 4) of a base portion of the endportion 21 e (the base of the end portion 21 e that is positioned on anextended line of the gear-side end surface 5 d of the outer race 5) isset larger than the diameter of an inner peripheral edge 21 f (the innerdiameter on the tip portion side) of the end surface 21 c of the endportion 21 e. With such a configuration, it is possible to enhance theeffect of rebounding the lubricant oil 16 dropping toward the endportion 21 e of the annular portion 21 b.

In FIG. 7, the diameter of the inner peripheral edge 21 g is set largerthan the diameter of the inner peripheral edge 21 f. However, thediameter of the inner peripheral edge 21 g is not limited thereto. Forexample, the diameter of the inner peripheral edge 21 g can be set to avalue equal to the diameter of the inner peripheral edge 21 f. In thecase of such a configuration, it is still possible to supply thelubricant oil 16 dropping toward the end portion 21 e of the annularportion 21 b, to the opening 4 a of the bearing 4 although the effect ofrebounding the lubricant oil 16 is reduced.

Similarly, the annular portion 22 b of the pinion bearing cap 22 isprovided inside the gear case 1 so as to extend parallel to the pinionshaft 9, and includes an end portion 22 e in which an end surface 22 cin an extending-direction is provided on the side of the pinion 10 withrespect to the extended line of the gear-side end surface 6 b of theinner race 6. Further, the diameter of an inner peripheral edge 22 g ofa base portion of the end portion 22 e is set larger than the diameterof an inner peripheral edge 22 f of the end surface 22 c of the endportion 22 e. With such a configuration, it is possible to enhance theeffect of rebounding the lubricant oil 16.

In FIG. 7, the diameter of the inner peripheral edge 22 g is set largerthan the diameter of the inner peripheral edge 22 f. However, thediameter of the inner peripheral edge 22 g is not limited thereto. Forexample, the diameter of the inner peripheral edge 22 g can be set to avalue equal to the diameter of the inner peripheral edge 22 f. In thecase of such a configuration, an oil supply from the opening 4 a of thebearing 4 is still possible, although the effect of rebounding thelubricant oil 16 is reduced.

Movement of the lubricant oil 16 is explained below. (a) The lubricantoil 16, sticking between teeth of the large gear 11, is pushed out toboth sides of the pinion 10 due to the meshing of the large gear 11 andthe pinion 10. (b) The lubricant oil 16, pushed out from the meshingpart 19, passes through the through hole 6 a formed in the inner race 6.(c) A part of the lubricant oil 16 pushed out from the meshing part 19,hits the side surface (the gear-side end surface 6 b) of the inner race6, and drops onto an inner peripheral surface 21 d of the end portion 21e of the annular portion 21 b (an inner peripheral surface 22 d of theend portion 22 e of the annular portion 22 b). The lubricant oil 16having dropped to the inner peripheral surface 21 d (22 d), is reboundedto the side of the bearing 4 because the end portion 21 e (22 e) isinclined toward the side of the bearing 4 and is then supplied from theopening 4 a of the bearing 4 to the interior of the bearing 4.

As explained above, the gear unit 100 according to the second embodimentincludes the pinion 10 that transmits a rotational force; the large gear11 that meshes with the pinion 10 and transmits a rotational force; thebearing 4 according to the first embodiment, which is located on each ofboth sides of the pinion 10; and the pinion bearing caps 21 and 22 thatare detachably fixed by the fastener 12 screwed into each of the surface1 a of the gear case 1 on the traction motor side and the surface 1 b ofthe gear case 1 on the opposite side to the traction motor side, andthat respectively include the annular portions 21 b and 22 b interposedbetween the gear case 1 and the outer peripheral surface 5 b of theouter race 5, and surrounding the outer peripheral surface 5 b. Theannular portions 21 b and 22 b are provided so as to extend from outsideof the gear case 1 to the inside in parallel to the pinion shaft 9 whileenclosing the outer peripheral surface 5 b of the outer race 5, and alsorespectively include the end portions 21 e and 22 e in which the endsurfaces 21 c and 22 c in the extending-direction are provided on theside of the pinion 10 with respect to the extended line of the gear-sideend surface 6 b of the inner race 6. Therefore, it is possible to supplythe lubricant oil 16, dropping toward the end portions 21 e and 22 e ofthe annular portions 21 b and 22 b, to the opening 4 a of the bearing 4.As a result, it is possible to use the bearing 4 for a longer period oftime.

Third Embodiment

FIG. 8 depicts an internal structure of the gear unit 100 according to athird embodiment of the present invention. Differences between the firstembodiment and the third embodiment are as follows. A plate 27 with atapered inner surface is mounted on each of the end surfaces 21 c and 22c of the annular portions 21 b and 22 b shown in FIG. 3. Elements of thepresent embodiment that are identical to those of the first embodimentare denoted by like reference signs and explanations thereof will beomitted, and elements different from the first embodiment are explained.

The plate 27 is provided on each of the end surfaces 21 c and 22 c ofthe annular portions 21 b and 22 b shown in FIG. 8. The plate 27 isconstituted to include a base portion 27 e that is fixed to each of theend surfaces 21 c and 22 c by a fastener 28 screwed from the inside intoeach of the end surfaces 21 c and 22 c, and an inclined portion 27 fthat extends from the base portion 27 e to the inside of the gear case 1and an end surface 27 b thereof is provided on the side of the pinion 10with respect to the extended line of the gear-side end surface 6 b ofthe inner race 6.

Further, the diameter of an inner peripheral edge 27 d of the baseportion 27 e is set larger than the diameter of an inner peripheral edge27 c of the end surface 27 b. In FIG. 8, the inner peripheral edge 27 cof the end surface 27 b is provided on the side of the pinion shaft 9with respect to an extended line of the outer peripheral surface 5 b ofthe outer race 5. With such a configuration, it is possible to enhancethe effect of rebounding the lubricant oil 16.

In FIG. 8, the diameter of the inner peripheral edge 27 d is set largerthan the diameter of the inner peripheral edge 27 c. However, thepresent invention is not limited thereto. An inner peripheral surface 27a of the inclined portion 27 f can be configured to be parallel to theextended line of the outer peripheral surface 5 b of the outer race 5.That is, the diameter of the inner peripheral edge 27 c can be set to avalue equal to the diameter of the inner peripheral edge 27 d. In thecase of such a configuration, an oil supply from the opening 4 a of thebearing 4 is still possible, although the effect of rebounding thelubricant oil 16 is reduced.

Movement of the lubricant oil 16 is explained below. (a) The lubricantoil 16, sticking between teeth of the large gear 11, is pushed out toboth sides of the pinion 10 due to the meshing of the large gear 11 andthe pinion 10. (b) The lubricant oil 16, pushed out from the meshingpart 19, passes through the through hole 6 a formed in the inner race 6.(c) A part of the lubricant oil 16, pushed out from the meshing part 19,also hits the side surface (the gear-side end surface 6 b) of the innerrace 6, and drops onto the inner peripheral surface 27 a of the inclinedportion 27 f. The lubricant oil 16, having dropped to the innerperipheral surface 27 a, is rebounded to the side of the bearing 4because the inclined portion 27 f is inclined toward the side of thebearing 4, and is then supplied from the opening 4 a of the bearing 4 tothe interior of the bearing 4.

The plate 27 according to the third embodiment can be configured asfollows.

In order to enhance the effect of rebounding the lubricant oil 16, it isdesirable that the inner peripheral surface 27 a of the inclined portion27 f is inclined toward the side of the bearing 4 as much as possible.Meanwhile, there are the rollers 7 on the side of the pinion shaft 9.Therefore, when attachment/detachment of the pinion bearing caps 21 and22 to/from the gear case 1 is considered, the inner peripheral edge 27 cof the inclined portion 27 f needs to be prevented from interfering withthe outer peripheral edge 7 d of the roller 7. That is, the diameter ofthe inner peripheral edge 27 c of the inclined portion 27 f needs to belarger than the outermost diameter of the roller 7 (the diameter of thearea where the outer peripheral edge 7 d of the large-diameter-side endsurface 7 b of the roller 7 comes into contact with the raceway surface5 a of the outer race 5). As described above, there is a trade-offrelationship between increasing the supply amount of the lubricant oil16 to the bearing 4 and ensuring assembling workability of the bearing4.

Therefore, the plate 27 shown in FIG. 8 is manufactured by usingshape-memory alloy or the like which changes its shape according to thetemperature. Further, the plate 27 is manufactured in order that thediameter of the inner peripheral edge 27 c of the inclined portion 27 fbecomes larger at a room temperature, and becomes smaller at atemperature higher than the room temperature, than the diameter of thearea where the outer peripheral edge 7 d of the large-diameter-side endsurface 7 b of the roller 7 comes into contact with the raceway surface5 a of the outer race 5. That is, the diameter of the inner peripheraledge 27 c is large enough to be capable of assembling the pinion bearingcaps 21 and 22 at a low temperature. However, the diameter of the innerperipheral edge 27 c is decreased under circumstances where it isnecessary to supply a large amount of the lubricant oil 16 to thebearing 4.

As a result, the inner peripheral surface 27 a of the inclined portion27 f is inclined at an angle not to interfere with the outer peripheraledge 7 d of the roller 7 at the time of assembling work. However, whenthe temperature of the lubricant oil 16 is increased due to the drivingof the gear unit 100, the inner peripheral surface 27 a is inclinedtoward the side of the opening 4 a in the bearing 4 according to theincrease in temperature of the lubricant oil 16. As described above, bymanufacturing the plate 27 from shape-memory alloy or the like, it ispossible to achieve both increasing the supply amount of the lubricantoil 16 to the bearing 4 and ensuring assembling workability of thebearing 4.

As explained above, the gear unit 100 according to the third embodimentincludes the pinion 10, the large gear 11, the bearing 4, the gear case1, and the pinion bearing caps 21 and 22 that respectively include theannular portions 21 b and 22 b. The plate 27 is provided on each of theend surfaces 21 c and 22 c of the annular portions 21 b and 22 b, and isconstituted to include the base portion 27 e that is fixed by thefastener 28 screwed from the inside into each of the end surfaces 21 cand 22 c, and the inclined portion 27 f that extends from the baseportion 27 e to the inside of the gear case 1. The end surface 27 b ofthe inclined portion 27 f is provided on the side of the pinion 10 withrespect to the extended line of the gear-side end surface 6 b of theinner race 6. Therefore, it is possible to supply the lubricant oil 16,dropping toward the inner peripheral surface 27 a of the inclinedportion 27 f, to the opening 4 a of the bearing 4. As a result, it ispossible to use the bearing 4 for a longer period of time, similarly tothe second embodiment. Further, it is possible to attach/detach theplate 27 by the fastener 28. Therefore, even when a structure change isrequired, replacement work can be performed at a low cost.

Further, in the gear unit 100 according to the third embodiment, theplate 27 is manufactured from shape-memory alloy. Furthermore, thediameter of the inner peripheral edge 27 c of the inclined portion 27 fbecomes larger at a room temperature, and becomes smaller at atemperature higher than the room temperature, than the diameter of thearea where the outer peripheral edge 7 d of the large-diameter-side endsurface 7 b of the roller 7 comes into contact with the raceway surface5 a of the outer race 5. Therefore, it is possible to increase thesupply amount of the lubricant oil 16 to the bearing 4, while ensuringassembling workability of the bearing 4.

In the first to third embodiments, an example in which the bearing 4,the pinion bearing caps 21 and 22, and the plate 27 are applied to agear unit for driving a railway vehicle has been explained. However, thebearing 4, the pinion bearing caps 21 and 22, and the plate 27 are alsoapplicable to a reduction gear mechanism incorporated in a vehicle suchas an automobile or an aircraft, and to a reduction gear mechanismincorporated in a general industrial device.

INDUSTRIAL APPLICABILITY

As described above, the present invention is mainly applicable to a gearunit, and is particularly useful as an invention that can stably supplylubricant oil to the interior of a bearing, regardless of the setting ona module of a gear and the setting on the number of teeth of a pinion.

REFERENCE SIGNS LIST

-   -   1 gear case    -   1 a surface on traction motor side    -   1 b surface opposite to traction motor side    -   4, 40 bearing    -   4 a opening    -   5 outer race    -   5 a, 6 c raceway surface    -   5 b, 7 c outer peripheral surface    -   6 g large-diameter-side flange portion    -   5 d, 6 b gear-side end surface    -   6, 60 inner race    -   6 a through hole    -   6 d small-diameter-side flange portion    -   6 e gear side opening    -   6 f roller side opening    -   6 h large-diameter-side flange surface    -   6 i, 21 d, 22 d, 27 a inner peripheral surface    -   7 roller (rolling body)    -   7 a small-diameter-side end surface    -   7 b large-diameter-side end surface    -   7 d outer peripheral edge    -   8 bearing cage    -   9, 9 a, 9 b pinion shaft    -   10 pinion    -   11 large gear    -   12, 28 fastener    -   13 shim set    -   14 intermeshing pitch line    -   16 lubricant oil    -   17 lubricant oil level    -   18 oil level gauge    -   19 meshing part    -   20 a, 20 b traction motor    -   21, 22 pinion bearing cap    -   21 a, 22 a inner peripheral portion    -   21 b, 22 b annular portion    -   21 c, 22 c, 27 b end surface    -   21 e, 22 e end portion    -   21 f, 21 g, 22 f, 22 g, 27 c, 27 d inner peripheral edge    -   23, 23 a, 23 b axle    -   24 a, 24 b flexible coupling    -   26 large-gear-side bearing cap    -   27 plate    -   27 e base portion    -   27 f inclined portion    -   30 truck frame    -   41 wheel    -   100, 100 a, 100 b gear unit

The invention claimed is:
 1. A reduction gear unit comprising: a pinionthat is fixed to a pinion shaft; a bearing that is located on each ofboth sides of the pinion; a large gear that is fixed to an axle, formedwith a diameter larger than a diameter of a pinion, and meshes with thepinion; a gear case that stores therein an amount of lubricant oil, andaccommodates therein the pinion and the large gear; and pinion bearingcaps each of which is detachably fixed by a fastener screwed into a sidesurface of the gear case, and includes an annular portion interposedbetween the gear case and an outer peripheral surface of an outer raceof the bearing and surrounding the outer peripheral surface, wherein aplate is provided on an end surface of the annular portion, and theplate includes a base portion that is fixed by a fastener screwed frominside of the gear case into the end surface, and an inclined portionthat extends from the base portion towards the inside of the gear caseto an end surface thereof which is provided on a same side as the pinionwith respect to an extended line of a gear-side end surface of an innerrace of the bearing, the bearing includes a tapered roller that includesa large-diameter-side end surface provided on a side of the gear, andthe plate is manufactured from shape-memory alloy, and is formed so thata diameter of an inner peripheral edge of the inclined portion becomeslarger at a room temperature, and becomes smaller at a temperaturehigher than a room temperature, than a diameter of an area where anouter peripheral edge of the large-diameter-side end surface of thetapered roller comes into contact with a raceway surface of the outerrace.
 2. The reduction gear unit according to claim 1, wherein adiameter of an inner peripheral edge of the base portion is larger thana diameter of an inner peripheral edge of the end surface.
 3. Thereduction gear unit according to claim 1, wherein a diameter of an innerperipheral edge of the base portion is equal to a diameter of an innerperipheral edge of the end surface.
 4. The reduction gear unit accordingto claim 1, wherein the inner race rotates integrally with the pinionshaft provided with the pinion, the outer race, and a plurality of therollers that are arranged rotatably between the inner race and the outerrace while maintaining a predetermined spacing to one another in arotation direction of the inner race, each of the rollers includes thelarge-diameter-side end surface that is provided on a side of the gear,and a small-diameter-side end surface that is provided on an oppositeside to the side of the gear, and is configured to have a shape taperedfrom the large-diameter-side end surface toward the small-diameter-sideend surface, the outer race includes a conical raceway surface that isprovided on an inner peripheral side, and that comes into contact withan outer peripheral surface of each of the rollers, the inner raceincludes a conical raceway surface that is provided on an outerperipheral side thereof and that comes into contact with the outerperipheral surface of each of the rollers, a small-diameter-side flangeportion that is provided on an opposite side to the pinion with respectto an extended line of the small-diameter-side end surface of each ofthe rollers, and a large-diameter-side flange portion that is providedon the side of the pinion with respect to an extended line of thelarge-diameter-side end surface of each of the rollers, and extends in adirection from the inner race to the outer race to be close to agear-side end surface of the outer race while enclosing thelarge-diameter-side end surface of each of the rollers, and forms anopening between the gear-side end surface and the large-diameter-sideflange portion, and in the large-diameter-side flange portion of theinner race, a plurality of through holes that are formed with apredetermined spacing to one another in a rotation direction of theinner race, and that connect from a gear-side end surface of the innerrace toward outer peripheral edges of the large-diameter-side endsurfaces of the rollers are provided.
 5. The reduction gear unitaccording to claim 4, wherein when a length from an inner peripheralsurface of the inner race to a gear side opening of each of the throughholes is represented as L1, and a length from the inner peripheralsurface of the inner race to a roller side opening of each of thethrough holes is represented as L2, each of the through holes has ashape satisfying a relationship expressed as L1<L2.
 6. The reductiongear unit according to claim 4, wherein when a length from an innerperipheral surface of the inner race to a gear side opening of each ofthe through holes is represented as L1, and a length from the innerperipheral surface of the inner race to a roller side opening of each ofthe through holes is represented as L2, each of the through holes has ashape satisfying a relationship expressed as L1=L2.